Re: [Boost-users] Using lambda for sort

From: chun ping wang (cablepuff_at_[hidden])
Date: 2007-08-08 12:11:25

maps are sorted base on key. I think his trying to sort the value. ..

Alternative solution.

/* ugly coding */
template <template <typename ELEM,typename = std::allocator<ELEM> >
         class CONT,
         class T, class U>
inline CONT<U> getValues(const boost::unordered_map<T, U>& data)
{
    CONT<U> retCont;
    typedef typename boost::unordered_map<T, U>::value_type value_type;
    BOOST_FOREACH(value_type val, data)
    {
        retCont.push_back(val.second);
    }
    return retCont;
}

std::vector<int> countriesValue = getValues<std::vector, int,
int>(countries);
std::sort(countriesValue.begin(), countriesValue.end());

On 8/8/07, Cory Nelson <phrosty_at_[hidden]> wrote:
>
> On 8/8/07, Olaf van der Spek <olafvdspek_at_[hidden]> wrote:
> > Hi,
> >
> > I'm trying to sort a map based on second, but I get all kinds of
> > compiler errors and I have no idea what's wrong. A simple _1 > _2
> > works fine, but that compares the maps themselves.
> >
> > Also, is there a better way to write the copy from map to vector or to
> > sort the map in general?
>
> maps are already sorted!  see the third template argument.  a simple
> vec.insert(vec.end(), map.begin(), map.end()) will copy it.  did you
> need something else?
>
> --
> Cory Nelson
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